Laserfiche WebLink
Canteen Facility November 20, 2000 <br /> Quarterly Groundwater Monitoring Report Page 3 <br /> • <br /> GROUNDWATER CONDITIONS <br /> The following sections summarize the local groundwater gradient and the groundwater analytical <br /> results <br /> Groundwater Gradient <br /> Interpretation of the monitor well gauging data indicates that there is a south - <br /> southwesterly hydraulic gradient across the Site of approximately 0 002 feet/foot <br /> Appendix A, Figure 2 presents the groundwater gradient map prepared by Ground Zero, <br /> Inc , for this gauging event The gradient appears to be consistent with past gauging <br /> events The drop in water levels is a result of fluctuations in groundwater elevations due <br /> to conditions of drought and the proximity of the site to the Stockton Diverting Canal <br /> The canal is located 1000' to the northeast The historical groundwater elevations are <br /> summarized on Table I <br /> Groundwater Anal ical Results — Contaminant Concentrations <br /> Groundwater quality data are compared to the California Department of Health Services <br /> Drinking Water Standard Maximum Contaminant Levels (CAMCL) Analysis of the <br /> seventeen groundwater samples obtained from the on-Site monitor wells indicated the <br /> following <br /> • Benzene was detected in groundwater samples from monitor wells MW-3, MW- <br /> 3A, MW-3D, MW-10, MW-13, and MW-13A at concentrations ranging from 0 7 <br /> to 21,000 µg11 The CAMCL for benzene is 10 µg/1 Benzene concentrations <br /> exceed the CAMCL in MW-3, MW-3B, MW-13 and MW-13A The benzene <br /> concentrations in MW-3 and MW-13 have increased since March 2000 However, <br /> the concentrations have decreased in MW-10 since March 2000 <br /> • Toluene was detected in monitor wells MW-31), MW-13, and MW-13A at <br /> concentrations ranging from 1 2 to 35,000 µg/1 The CAMCL for toluene is 150 <br /> µ.g/1 Toluene concentrations only exceeded the CAMCL in MW-13 <br /> Concentrations of toluene increased in MW-31) and MW-13, and decreased in <br /> MW-13A <br /> • Ethylbenzene was detected in monitor wells MW-3D, MW-13 and MW-13A at <br /> concentrations ranging from 2 to 3,200 µg11 The CAMCL for ethylbenzene is 700 <br /> µg/l, which was exceeded only in MW-13 <br /> . • Xylenes were detected in monitor wells MW-31), MW-13 and MW-13A at <br /> concentrations ranging from 3 4 to 18,000 µg/1 The CAMCL for xylenes is 1,750 <br />